Answer:
210
Explanation:
This study must include each N₁, and it has to be done at each N₃, using each N₂, while carried out by each N₄ ⇒ that means that the total number of possibilities:
N₁ x N₃ x N₂ x N₄ = 3 x 7 x 5 x 2 = 210
The total number of test runs is 210.